Commonly implemented or studied biometric modalities include fingerprint, face, iris, voice, signature and hand geometry. Many other modalities are in various stages of development and assessment. There is not one biometric modality that is best for all implementations. Many factors must be taken into account when implementing a biometric device including location, security risks, task (identification or verification), expected number of users, user circumstances, existing data, etc. It is also important to note that biometric modalities are in varying stages of maturity.